Analyses of cat, rat and human retinas are in progress to determine the effects of aging on retinal neurons. Rat and human retinas are being accumulated, as well as the medical histories of the human eye donors. Selection of retinas which will demonstrate aging rather than other processes is made based on these histories. An analysis of general fixation quality has determined an acceptable delay between death and enucleation, and enucleation and fixation for human eyes and guidelines drawn up for the Eye Bank to provide optimal specimens for these investigations (Eyes enucleated within 6 hours of death have acceptable fixation; the time between enucleation and fixation is less important). Certain diseases and drugs appear to be detrimental to retinal structure. In human retinas there is a trend for outer segment length to be reduced in older individuals. There is also a clearcut reduction in light transmittance through the lenses of aged eyes which can be associated with aging. A collateral study has shown that Bruch's membrance collagen is more robut in blacks than in whites. This may be related to the lower incidence of senile macular degeneration in blacks. This study is in progress in eyes from age and sex-matched blacks and whites.